Researchers have tried to produce a white persistent phosphor by blending a blue persistent phosphor, a green persistent phosphor and a red persistent phosphor. However, this approach is problematic because each of the persistent phosphors decays at a different rate, causing a color change with time, the blend is of low intensity and is not long persisting within the white color regime.
Phosphor compositions based on (Ba, Sr, Ca)Al2O4:Eu+2, Dy+3 have been known to produce a high efficiency long persistent green emission color. Also, compositions based on (Ba, Sr, Ca)Al2O4:Eu+2, Nd+3 have been known to produce a high efficiency long persistent blue emission color. However, producing a high efficiency, long persistent white phosphor remains elusive.